1. Field of the Invention
The present invention relates to a laser beam printer or another printing apparatus which prepares bit map data from intermediate data before printing, and a printing control device and a memory management method which are used in the printing apparatus.
2. Related Background Art
There are widely used printing apparatus which receive data (printing data) representing contents to be printed and a printing format from a host computer or the like, prepare from the received data a bit map to be actually outputted (hereinafter, referred to as rendering) and print/output the bit map on, for example, a sheet of paper (hereinafter, referred to as shipping).
In the printing apparatus of the type rendering and thereafter shipping an output bit map of one page, a memory for holding the output bit map of one page is essential. This results in a disadvantage that the memory capacity must be increased, particularly, in a printing apparatus with a high degree of output resolution or the like; hence the apparatus are very expensive.
There are also printing apparatuses of the (banding process) type that one page is divided into a plurality of smaller units (bands), and a bit map of one band is rendered and thereafter shipped. In the apparatuses, a rendering process for the next band is performed in parallel with a shipping process for the previous band. Such printing apparatuses have a disadvantage that if the rendering time of the next band is longer than the shipping time for the previous band in the parallel process, a print overrun phenomenon occurs.
Another disadvantage is that because a memory for holding the printing data of one page is required in addition to the memory for holding the rendered bit map, the printing data of one page cannot be processed (hereinafter referred to as the memory deadlock) if the memory capacity is deficient.